Clopyralid, 3,6-dichloropicolinic acid, is an herbicide used to control broadleaf weeds in cereal crops, pasture, fallow, forest and industrial situations. Various formulations are currently marketed, many of which are aqueous solutions that are normally diluted prior to use. Typically the clopyralid is provided as an amine salt, which exhibits sufficiently high solubility in water to provide an aqueous concentrate herbicidal formulation (SL). Typical commercial formulations of clopyralid have an active loading of from about 300 grams acid equivalent per liter (gae/l) to about 450 gae/L of the monoethanolamine (MEA) or triisopropanolamine (TIPA) salts. Lontrel® herbicide (registered trademark of Dow AgroSciences LLC) is sold as a 360 gae/L SL formulation of the monoethanolamine salt of clopyralid in water and is used for the control of broadleaf weeds in turf and ornamentals.
High-strength formulations are desirable for a variety of economic and environmental reasons. For example, it is desirable to provide a high-strength concentrate in order to reduce shipping and handling costs and to reduce the amount of packaging material that must be disposed after use of the product. The high-strength concentrates should be stable and retain potency during storage and shipping. Furthermore, the high-strength concentrate should be a clear, homogeneous liquid that is stable at temperatures at least as high as 54° C. and should not exhibit any precipitation of solids at temperatures as low as −10° C.
There is a continuing need for new, high-strength SL herbicidal formulations that exhibit low viscosity and stability at low temperatures.